The present invention relates to components for overcasting, moulded objects into which those components are overcast, and manufacturing processes of moulded objects. A choice application of the invention is the manufacture of covers or seats for cars or planes.
To equip a part in a plastic material, such as a polyurethane part constituting a cover, with a component for overcasting so as to equip this cover with means of fixation, a known method is to apply a component for overcasting with a base on both sides of a cavity arranged at the bottom of a cast.
Fixating elements are to be found on the underside of the base. A magnet is to be found at the bottom of the cavity, whereas a metallic layerxe2x80x94which can be attracted by the magnetxe2x80x94is deposited on the upper side of the base.
A layer of foam is applied by glue between the base and both sides of the cavity standing out at the bottom of the mould, in order to ensure that the cavity remains liquid-proof and that the fixating capacity of the fixating elements to be found therein is not altered by the liquid foam used to cast the polyurethane afterwards.
When the liquid foam used to cast the moulded object is poured, its weight crushes the foam which ensures that the cavity remains liquid-proof. The assembly procedure in the mould is fast and the liquid-proofness is appropriate, but the manufacturing is complicated. Notably, in order to apply foam around the underside of the base, the fixating elements of the base features must be crushed at first.
The inconvenience can be remedied with equipping the base with two ramps at each opposite side of the base, jutting upwards and away from one another.
The base is maintained in the cavity, with placing the entire base and its ramps within this cavity. A small flexion of the ramps allows for clasping them to the inside vertical sides of the walls that form the cavity at the bottom of the mould.
The flexion by clasping of the ramps ensures the cavity remains liquid-proof, but the clasping is a time-intensive operation.
The aim of the invention is to remedy these inconveniences with a component for overcasting that does not necessitate crushing the fixating elements at its periphery, nor applying layers of glue and foam, nor clasping ramps to the auxiliary cavity at the bottom of the mould in the assembly procedure.
This simplifies and speeds up the assembly in the mould, without complicating the manufacturing of the component for overcasting itself as before. Furthermore, the invention simplifies the casting of the base and ensures the moulded object is firmly adhered with the base.
The component for overcasting includes a base, flexible elements are to be found on the underside of the base. Two ramps jut upwards and away from two opposite lateral sides of the upperside of the base.
According to the invention, material which can be attracted by a magnet is applied on the upper side of the base.
In order to manufacture the moulded object, the ramps of the component for overcasting are laid on the two walls situated at the bottom of the mould, between which a magnet is fixated at the bottom of the mould. This is in order for the material which can be attached by a magnet to be efficiently attracted by the magnet at the bottom of the mould and the component for overcasting to be well maintained on the ramps. Thus, resulting in an appropriate liquid-proofness.
The mould is then filled with a liquid plastic material, which is then left to solidify, end the moulded object is then cast.
Any clasping is therefore eliminated, whilst appropriate liquid-proofness is ensured by the magnetic attraction, without the need to deposit a supplementary layer of foam and a layer of glue between the walls and the sides of the component for overcasting, nor especially crushing the fixating elements situated at the periphery of the base.
The base is usually a plastic material, for instance of a thermoplastic type, notably in polypropylene, polyamide, etc. Steel powder mixed in with polymer resins can be used as the material that can be attracted by a magnet, notably in a ratio of forty/sixty percent of the weight to seventy/thirty percent of the weight.
In a preferred invention, the free edges of the ramps feature a lip jutting outward.
When the base is placed, these lips are higher than the top of the walls so that, when the moulded object is cast, some of the liquid material not only deposits on the upper side of these lips, but also on part of their underside.
A part of the object is therefore in contact with the underside of the ramps and is well maintained by the base, without it being necessary to implement particular fixating elements and without it preventing an easy casting of the base, since the lips are cast with it, it is however possible to also implement fixating elements on the upper side of the base and lips jutting inward from the free edges of the ramps, to achieve a similar purpose.
The ramps may not be flat. They will preferably feature an angle of ninety degrees to one hundred and seventy degrees between them.
A moulded object is therefore obtained, which includes a main body cast in a plastic material and to which is fixated, by casting, a component for overcasting according to the invention.
The body may be in a plastic material compatible with that of the component for overcasting, ie which manages adherences between the body and the base during the casting in the mould. The possibility exists however, to extend the range of plastic materials to be used for the body and the component for overcasting, as part of the body is in contact with the underside of the ramps and therefore creates a fixation.
Polyurethanes can be used as a material for the body. Most often, the body is in a material different to that of the base, in order to respectively equip each with the best suited properties, for instance the elasticity of the filling foam for a cushion and the rigidity for a fixating component.
A component for overcasting can be manufactured by extrusion, for instance using the same process as described in the European patent No 0 657 118 in the name of Kuraray Co. Ltd., which is incorporated hereby by reference.